Fuel injector for internal-combustion prime-movers



Sept. s, 1936. G. AMER 2,053,312

FUEL INJECTOR FOR INTERNAL COMBUSTION PRIME MOVERS Filed July 2, 1935 2S heets-Sheet'2 g I c;

m w N mvENToR I Patented Sept. 8, 1936 FUEL nvJEc'roR FOR INTERNAL-COM- BUs'rroN .rnIME-MovERs George Amery, Kilburn, London, England Application .t'uly 2, 1935, Serial No. 29,503 lln Great Britain August 8, 193% Z Claims.

This invention comprises improvements in or 'relatingto fuel injectors for internal-combustion prime-movers and has for an object to provide a fuel injection system of an improved type for an internal-combustion engine.

According to one feature of the present invention there is provided in a fuel injection system for an internal-combustion engine the combination of a fuel-pump. a fuel-nozzle through which fuel can be injected into a combustion chamber, a conduit for conveying fuel from the pump to the nozzle, a spring-closed valve for closing said conduit, a piston operatively connected .to said valve for opening it under the fuel pressure and a stop for limiting the lift of the valve. By this means, if the stop is adjusted so as to allow a very limited lift atomization takes place at the seating of the valve and a second atomization at the nozzle orifice.

A relief-valve may also be provided for permitting escape of fuel from the conduit after the valve-movement has been terminated by the stop. I

The efiect of employing a system as just described is that injection commences at a predetermined pressure which is settled by the force required to open the valve'under the influence of the piston. When further lift of the valve is prevented by the stop a rise of pressure will take place but the amount of this rise is limited by the reliei'walve. Consequently injection commences at a certain pressure and rises to a second pressure at which it is. kept. This ensures a more or less gentle start for the ignition followed by a more vigorous period when combustion has well commenced and tends to obviate knocking. 1

Fuel pumps are commonly provided on internal-combustion engines of the fuel injection type. Conveniently the parts other than the fuel-pump are according to the present invention combined in a single fuel injection device. The invention accordingly includes in a. fuel-injection device for an internal-combustion engine the combination of a nozzle orifice, a fuel-passage leading to the orifice, a valve seating at the back of the fuelpassage, a spring-closed valve therefor, a conduit for conveying fuel under prwsure to the valve,

a piston subject to the fuel pressure and oper-' by an annular gap around the said extension. The wall of the fuel-passage surrounding the said stem may be made of increasing diameter from the orifice inwardly so that :when the valve is lifted the extension moves into a larger portion of the fuel-passage and the area of the orifice is increased. This tends to permit obstruction to be cleared. Moreover, the annular shape of the orifice ensures that it is unlikely the orifice will become even momentarily obstructed over any considerable portion of its area by any accidental solids which may be suspended in the fuel.

The following is a description, by way of example, of certain constructional embodiments of the invention, with reference to the accompanying drawings, in whichz- Figure 1 is a vertical section through a. fuelpump and. nozzle, and

Figure 2 illustrates a modified construction.

Referring to Figure 1 a pump-barrel ll contains a plunger 52 having a head l3 outside the barrel which carries a cam roller l4 actuated by a cam I5 on a shaft Hi. The plunger I 2 is returned against the action of the cam by a spring ll. It will be appreciated that the drawings are diagrammatic in the sensethat well known constructional precautions such as the provision of packing rings or sealing grooves around the plunger are not illustrated. The pump-barrel communicates through a passage I8 with an inlet valve whichmay be, for example, a springclosed ball valve of the pattern commonly employed for liquid pumps of small capacity. In addition the plunger is in communication through a permanently open passage I9 with a fuel-nozzle. The fuel-nozzle comprises a nozzle proper 20 having an injection orifice 2 land a body portion 22 which forms a guide for a needle-valve 23. The needle-valve has a conical seating 24 for closing the back of the nozzle aperture, it has '40 an enlargement or shoulder 25 hereinafter referred to and a closing piston 26 at the back of the body 22. Moreover, the stem of the needie-valve 23 is prolonged at 21 and carries outside the back of the body of the fuel-nozzle a 5 head 28 on which bears a closing spring 29 located in a screwed cap 30. By screwing the cap backwards-oniorwards upon the body of the fueln'o z'zlfe the degree of compression imparted to the spring 28 eanbe varied. The cap may be locked by alock-nut I30. The cap 30 furthermore contains a screwed stop 3| having a square 32 on its head for adjustment purposes and adapted to be set so asto limit the degree of opening of the needle-valve 23. Returning to the seating end' 'oi of the needle-valve, it will be observed that owing to the action of the stop 3| only a very small lift of the seating 24 from the back of the nozzle is permitted. Between this seating and the fine nozzle-orifice 2| there is a relatively enlarged cylindrical passage 33. I

From one side of the permanently open passage between the pump-barrel II and the fuel-nozzle there is a branch passage 34 which contains a fuel-pressure relief-valve 35 held down by a spring 36 on a seating 31 by means of an internally screwedand adjustable cap 38.

At one side of the pump-barrel ll there is a guide 39 fora piston-valve 40, the stem of which carries a head 4| having a roller 42 to engage on a cam 43. The cam 43 is driven by a gear wheel 44 from another gear wheel 45 on the shaft IS, the operative connections being such that the timing of the piston-valve can be varied relatively to the timing of the pump-plunger. ton-valve constitutes a mechanically-actuated valve for regulating the opening and closing, or at least the closing of the needle-valve 23. The piston-valve is normally kept with its roller 42 pressed against the cam 43 by a spring 46.- Into the side of the piston valve chamber there open a port 41 from the pump-barrel II, and a port 48 leading to a passage 49 which terminates in a chamber in the body 22 of the fuel-nozzle, in which chamber'works the closing piston 26. There is, in addition, a port 50 which is open to the atmosphere. Owing to the disposition of the ports through which piston-valve 40 is lowered the passage 49 is connected through the port 58 to the atmosphere, but when the piston-valve is raised connection to the atmosphere is shut off and the port 41 from the pump-barrel is connected to the port 48 and the passage 49. In the operation of this device the cam I5 is so operatively connected to the internal-combustion engine with down so that'theport 41 is shut. As soon as the pressure is risen to a suflicient value the pressure acting on the shoulder of the injection valve 24 becomes suiiicient to lift the valve against the spring 29 and injection commences. There is a preliminary atomization in the narrow coni cal space betweenthe needle-valve seating 24 and the nozzle 20, this space being set so as to be of the order of a few thousandths of an inch only. Therefore there will be expansion and atomization into the space 33 before the fuel-nozzle proper is reached. Thereafter there is a further expansion through the nozzle proper 2 I and highly atomized fuel enters the combustion chamber of the engine. Meanwhile the pump-plunger continues to rise and the injection pressure is keptup but is prevented from rising above a predetermined value by the relief-valve which sets an upper limit to the injection pressure. The spring 29 sets a lower limit and injectionmust, therefore. take place at a pressure which lies between that set by the spring 29 and thatset by the spring 35. If the timing of the cam 43 is delayed sufllciently late the fuel-plunger will come to the end of its stroke and will commence to return.

The pis- Shortly after the commencement of the return stroke the fuel in the fuel-nozzle will lose its pressure owing to the flowing of the oil back into the working cylinder, and the spring 29 will close the needle-valve again upon its seating 24. Thus the variations of pressure in the pump-barrel determine the opening and closing of the valve without any interposed valve mechanism. Assuming, however, as will be the case except when the maximum injection period possible is being operated, that the cam 43 comes into operation before the end of the delivery stroke of the pumpplunger, then in that case the piston valvewill be raised and oil under pressure will pass through the port 48 and passage 49 to the needle-valve closing piston 26, and as this is of greater area.

thanthe shoulder 25 which serves as an opening piston, the needle-valve will be shut, notwithstanding the fact that pressure continues at the seating 24. By arranging that the mechanism which interconnects the shaft l6 with the cam 43 is capable of variable timing, it will be seen that a variable injection period with a short termination in secured in this way without any complication of the valves between the pump-barrel II and the nozzle chamber. Such valves are objectionable as they lead to loss of oil pressure and are diiiicult to maintain in order.

Referring to Fig. 2, this shows a modification of the fuel-pump and injection-nozzle, the barrel II and plunger [2, casing 39 and valve 40 being provided and actuated as before. There is a pipe 10 leading to the front end of the injection-nozzle II from the pump-barrel and a pipe 88 leading from the valve 48 to a closing piston. Although these pipes are shown in the drawings as quite short it is tobe understood that they might be of any desired length and that the same is true of the interconnections shown in Figure 1.

Between the pump-barrel H and the casing- 39 there is an inlet-valve '12 connected-to an inlet-port 13, which port corresponds to the port l8 in Figure 1.

The body of the fuel pump is in two parts H and 14 which are screwed together by a nipple 15 between them and both parts of the body are bored through axially to receive a needlevalve I6 which is pressed upon a seating 11 by a spring I8. The needle-valve carries a cylindrical extension 19 beyond the seating 11 and the extension almost fills a nozzle aperture 89 between which and the plug-like extension there is a narrow annular gap which may be only of the order of one or two thousandths of an inch wide or even less. This gap constitutes the effective nozzle-orifice and the extension 19 and the end of the nozzle are arranged to be flush with one another when the nozzle is shut. The nozzle-orifice widens conically as one proceeds backward from the front face of the nozzle, leaving a definite annular passage 8| around the extension 19, and between it and the seating 11. Behind the seating 11 the needle-valve has a shoulder 85 which corresponds to the shoulder 25 of Figure 1. Around the needle-valve, behind the shoulder 85, there is a sleeve-like relief valve 82 which presses on a relief-valve seating 83 and is held up to its work by a spring 84. The relief-valve is grooved-longitudinally at 86 to provide a passage for carrying away oil should the valve lift, and this passage is continued by an internal groove 81 in the nipple 15 to a relief-valve passage 88 connected at 89 to the atmosphere by a transverse bore. The passage 89 to the atmosphere may, if desired, be provided with a nipple for attachment to a drain pipe instead of opening directly to the atmosphere.

The head 90 of the needle-valve 19 serves as a closing piston as well as receiving the pressure of the spring I8. The head 90 is hollowed out to receive the end of a stem 9! co-axial with it, and the stem 9| is pressed normally forward as far as possible in the nozzle casing M by a spring 92 held in place. by a cap 93. The cap 93 contains also a screw stop 94 corresponding to the 1 stop 3| of Figure 1. This is secured by a locknut 95. It will be observed that the oil passage 89' for closing the needle-valve is connected to 1 a space around the spring 18 so that oil pressure admitted through 99 will bear upon the head 9@ of the needle-valve to close it. There is a very small gap 96, not amounting to more than one or two thousandths of an inch or even less between the stem 9i and the head 99, and there 'is another similar gap 97 between the stem 9i and the stop 99. The stem 9i is hollow, containing a central passage-way 98 which communicates with the space 99 around the spring 92, and is thence connected to the atmospheric outlet 39.

The atmospheric outlet 99 is also connected by a branch N39 to the space at the end of the piston-valve 59, and the piston-valve 69 contains two ports Hi2, I99. One of these serves, when the valve is raised, to connect the pipe til with the oil pressure in the pump-barrel ii and the other port I92 serves, when the valve is lowered to connect the pipe 99 with the branch W9 and thence to atmosphere.

In the operation of this nozzle, as the pumpplunger l2 rises it causes a rise of oil pressure in the pipe H! which lifts the needle-valve it off its seating 'll owing to the action of the pressure on the shoulder 25. The pressure atwhich this lifting of the needle-valve occurs isdetermined by the spring 18 and constitutes the initial injection pressure. The amount of the lift is limited by the amount of the gap 96 and is such that preliminary atomization occurs at the seating 11 followed by expansion in the space 9|, and further atomization through the fine annular orifice 89. Any further rise in fuel pressure serves to lift the needle-valve somewhat further off its seating, but the total lift is limited by the stem 9| closing the gap 91 and coming against the stop 94. This total lift is made such as not toprevent atomization at the seating 11, but it will be observed that owing to the conical construction of the nozzle-orifice 89 the increase in area at the seating 11 is accompanied by an increase in area of thenozzle-prifice 89 so that the balance of expansion at the seating and the orifice is maintained. If any further rise of injection pressure occurs it may be su'fiicient to lift the relief-valve 82 and assist. the excess fuel to escape through the passages 86, 81 to the atmosphere at 89. Thus the maximum injection pressure is limited as before. Either by the termination of the movement of the plunger l2 or by the operation of the valve 40 the needle-valve is thereafter closed as already described I claim:-

1. A fuel-injection device for an internal-combustion engine comprising 'in combination a nozzle-orifice, a fuel passage leading to the orifice,'a valve seating at the backof the fuel passage, a spring-closed valve therefor, a conduit for conveying fuel under pressure to' the valve, a piston subject to the fuel pressure and operatively con-' nected to the valve to lift it from its seating, a stop for limiting the lift of the valve and where- -in the valve carries an extension beyond its zle-orifice, a fuel passage leading to the orifice, a valve seating at the back of the fuel passage, a

spring-closed valve therefor, a conduit for conveying fuel under pressure to the valve, a piston subject to the fuel pressure and operatively con nected to the valve to lift it from its seating, a stop for limiting the lift of the valve and wherein a relief-valve is also provided in the form of a sleeve surrounding a stem .of the spring-closed valve and is held on its seating by a spring also surrounding said valve stem, said relief-valve being subject to the fuel pressure and communicating when opened with a fuel escape orifice.

3. A fuel-injection device for an internal-combustion engine comprising in. combination a nozzle-orifice, a fuel passage leading to the orifice, a valve seating at the back of the fuel passage, a spring-closed valve therefor, a conduit for conveying fuel under pressure to the valve, a piston subject to the fuel pressure and operatively connected to the valve to lift it from its seating, a stop for limiting the liftof the valve and wherein the stop is itself spring-supported and given a limited freedom of movement up to a second stop for the purpose described.

4. A fuel-injection nozzle for an internal-combustion prime-mover comprising a nozzle body and a needle-valve therefor (the nozzle body having aninjection orifice into the cylinder and the needle-valve having a seating within the nozzle body which closes a passage leading to the fuel orifice) and a plug on the needle-valve projecting forwardly from the seating into the nozzle-orifice, which plug is of such diameter as to afford between itself and the walls of the nozzle-orifice an annular passage of the area required for the injection opening, and wherein the tip of the plug on the needle-valve is made to coincide at its terminus with the plane of the nozzle face through which the fuel enters the combustion chamber of the prime-mover and the surrounding nozzle-orifice is enlarged behind the face in a stepped or tapered formation so that as the needle-valve moves rearwardly the tip of the plug opens into a wider space.

5. In a fuel injector for an internal-combustion prime mover, the combination of a fuelpump, a

fuel nozzle having an orifice through which fuel can be injected into a combustionchamber, a fuel conduit for conveying fuel from the pump to the nozzle, a spring-closed valve for closing said conduit, afuel passage between the springclosed valve and the nozzle-orifice, saidpassage being of greater cross-sectional area than the nozzle-orifice and than the area between the valve and its seating when open, so that fuel is fuel therefrom, said valve being set to open at normal maximum injection pressure.

6. In a fuel injector for an internal-combustion prime mover, the combination of a fuel pump, a fuel-nozzle through which fuel can be injected into a combustion chamber, a fuel-conduit for conveying fuel from the pump to the nozzle, a spring-closed valve for closing said conduit, a piston subject to the fuel pressure and operatively connected to said valve for opening it under the fuel pressure, a stop for limiting the lift of the valve so set as to'ensure the valve contacting with it under the injection pressure and a relief valve (for permitting escape of fuel from the conduit) which is set to open at normal maximum injection pressure, said relief valve having the form of a sleeve surrounding a stem of the spring closed valve of the nozzle and' held on its seating by'a spring also surrounding said valve stem.

I. In a fuel injector for an intemal-combustion prime mover the combination in one unit of a fuel nozzle through which fuel can be injected into a combustion chamber, a fuel conduit leading to the nozzle, a spring-closed valve for closing said conduit, a piston subject .to the fuel pressure and operatively connected to said valve for opening it under the fuel pressure, a stop for limiting the lift of the valve so set as to ensure the valve contacting with it under the injection pressure and a relief valve (for permitting escape of fuel from the conduit) which is set to open at normal maximum injection pressure, said relief valve being in the form of a sleeve surrounding a stem of the spring-closed valve of the nozzle, and held on its seating by a spring also surrounding said valve stem. I

GEORGE AMERY. 

